Furnace?

[mmm240]

When my furnace turns off, a few seconds later the blower turns back on for a minute. It's an old furnace (probably more than 20 years old) but it blows good heat! I want it to last quite a while longer, but this worries me.

Anyone have any ideas?

[mmkeller]

Not an expert but I've been told this is to clear out any residual warm air left in the ducts. Mine is old and does the same thing

[mmm240]

Makes sense, but it didn't used to do this. I'm thinking my blower should be running longer than the furnace naturally, but isn't. And don't know how to adjust this.